bcm2835_stream.cpp

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#ifdef bcm2835
 
#include <cstring>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include "bcm2835_stream.h"
 
uint32_t millis()
{
    struct timeval now;
    gettimeofday(&now, NULL);
    return (uint32_t) ( now.tv_usec / 1000 );
}
 
Stream::Stream(const char* port)
{
    Stream::port = port;
}
 
void Stream::begin(unsigned long baud, int flags)
{
    termios options{};
 
    fd = open(port, flags);
    if (fd == -1) {
        printf("[ERROR] UART open(%s)\n", port);
        return;
    }
    fcntl(fd, F_SETFL, O_RDWR);
 
    #if 1
 
    speed_t myBaud;
    switch ( baud )
    {
        case    9600:   myBaud =    B9600; break;
        case   19200:   myBaud =   B19200; break;
        case   38400:   myBaud =   B38400; break;
        case   57600:   myBaud =   B57600; break;
        case  115200:   myBaud =  B115200; break;
        case  230400:   myBaud =  B230400; break;
        case  460800:   myBaud =  B460800; break;
        case  500000:   myBaud =  B500000; break;
        case  576000:   myBaud =  B576000; break;
 
        // The TMC2209 maxed out around 750kbaud so other enums after 576kbaud is not needed.
 
        default:
            printf("[ERROR] UART invalid baud: %ld for port: %s\n", baud, port);
            return;
    }
 
    tcgetattr(fd, &options);
 
    cfmakeraw( &options );
    cfsetispeed( &options, myBaud );
    cfsetospeed( &options, myBaud );
 
    // See: https://www.mkssoftware.com/docs/man5/struct_termios.5.asp
    // Use 8 data bit, no parity and 1 stop bit
    // Set bits per byte
    options.c_cflag |= ( CREAD | CLOCAL ) ;   // turn on READ and ignore modem ctrl lines
    // CBAUDEX no need to use extended baud; setting this for some reason shows incorrect timing on the oscilloscope for 9600 but OK for 57600
    // Not setting it seems to be OK on the oscilloscope for both 9600 and 57600.
    options.c_cflag &= ~PARENB;     // no parity
    options.c_cflag &= ~CSTOPB;     // 1 stop bit
    options.c_cflag &= ~CSIZE;      // reset number of bits mask
    options.c_cflag |= CS8;         // 8 data bit
    options.c_cflag &= ~CRTSCTS;   // no flow control
 
    options.c_iflag &= ~(IXON | IXOFF | IXANY); // turn off s/w flow ctrl
    options.c_iflag |= IGNPAR;       // ignore characters with parity errors
 
    options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG) ;    // make raw
 
    options.c_oflag &= ~OPOST;  // make raw
 
    // See: http://unixwiz.net/techtips/termios-vmin-vtime.html
    options.c_cc[VMIN]  = 0;
    // Cannot set VTIME to 0 as it creates more problems such as cannot read the driver properly.
    // Also, you do not want to set to 100 because it is a blocking read and timeout in VTIME and can take up to 10 seconds and
    // if retries are implemented in caller then it feels like something is blocking for N retries x VTIME.
    options.c_cc[ VTIME ] = 10;      // VTIME defined as tenths of a second so 100 is actually 10 seconds; and 10 deciseconds is 1 second.
 
    tcflush(fd, TCIOFLUSH); // flush both tx and rx
 
    #else
 
    // Use 8 data bit, no parity and 1 stop bit
    tcgetattr(fd, &options);
    options.c_cflag = CS8 | CLOCAL | CREAD | CBAUDEX;
    options.c_cflag &= ~CBAUD;  // use the extended baud
    options.c_cflag &= ~PARENB; // no parity
    options.c_cflag &= ~CSTOPB; // 1 stop bit
    options.c_iflag = IGNPAR;
    options.c_oflag = baud;
    options.c_lflag = baud;
 
    tcflush(fd, TCIFLUSH);
 
    #endif
 
    tcsetattr(fd, TCSANOW, &options);
 
    // Maybe add 10ms delay (belt and braces) to let UART setup correctly
    const int DELAY_MS_10 = 10;
    usleep( 1000 * DELAY_MS_10 );
}
 
void Stream::end()
{
    ::close(fd);
}
 
int Stream::available()
{
    int result;
    if (ioctl(fd, FIONREAD, &result) == -1)
        return -1;
    return result;
}
 
uint8_t Stream::write(const uint8_t data)
{
    return (uint8_t)::write(fd, &data, 1);
}
 
uint8_t Stream::read()
{
    uint8_t data = -1;
    if (::read(fd, &data, 1) == -1)
        return -1;
    return data;
}
 
Stream Serial("/dev/serial0");
Stream Serial1("/dev/serial1");
 
#endif // bcm2835